A previously unreleased film of President John F Kennedy's motorcade has revealed new details of the final moments before his assassination.

The silent film shows the president and his wife Jackie shortly before the fatal shot was fired.

Amateur photographer George Jefferies held onto the film for more than 40 years believing it was unimportant.

But Dallas museum curator Gary Mack says it is bound to provide new fuel to the conspiracy theorists.

Conspiracy theorists

The film shows the president's coat bunched up on his back - a detail some will see as evidence that the bullet wounds on the president's body did not match those on his jacket.

The film also shows "the clearest, best film of Jackie in the motorcade", says Mr Mack.

Also visible is secret service agent Clint Hill, riding on the back of the car. After the shots were fired, Mr Hill jumped onto the back of the vehicle and drove with it to the hospital.

The new film only came to light when Mr Jefferies mentioned it in conversation to his son-in-law, Wayne Graham, who persuaded him to donate it to the museum.

Mr Mack said: "Everyone who captured the motorcade before the assassination thinks their pictures are unimportant. But to historians, all photos and home movies are important to possibly answer questions that will be asked in the future.

"I've already seen the footage on a conspiracy web site."

He said since the president's jacket was riding high on his back, the entry wound in his body did not appear to match the expected position in his coat, which would add fuel to claims that more than three shots were fired.

There were at least 150,000 people lining the route of the motorcade and Mr Mack has encouraged anyone with film or photographs of the event to come forward.